Current approaches to medical education produce new physicians with insufficient clinical competency to practice effectively with limited supervision, which has serious implications for patient outcomes during hospital off hours. Up to 70% of patients admitted to a hospital are admitted on nights or weekends, when staffing is low and residents may be in charge of patient care. Off-hours care is linked to an increase in medical errors, surgical complications, and readmission rates. Negative patient outcomes during off hours are 2 to 8 times more likely to occur under the care of residents in their first postgraduate year. We propose to improve undergraduate medical education to minimize the time to clinical competency for first year residents through targeted diagnostic reasoning skill development that (1) integrates basic science and clinical instruction; (2) provides deliberate practice with structured, case-based learning opportunities; and (3) enables anytime/anywhere learning that fits with the demanding schedules of most medical students. Southern Illinois University School of Medicine (SIUSOM) is a recognized leader in using performance-based clinical competency exams to enhance reasoning skill acquisition among medical students. These exams feature clinical scenarios with standardized patients followed by diagnostic justification essays which require students to explicitly describe the thought process used to reach a final diagnosis. These essays are the most reliable method of assessing diagnostic strategies but are not in use in the majority of medical schools, though interest in improving diagnostic reasoning instruction and assessment during undergraduate medical education is widespread. Barriers to the widespread adoption of this approach are 1) the time-consuming need to hand score each essay; and 2) the difficulty in accurately and consistently identifying the causes of strategy failures. This project will develop an application to provide automated scoring of diagnostic justification essays, identification of the underlying causes of failure when students perform poorly, and feedback with instructional strategies for remediation specific to each deficit. We propose these specific aims: 1) Develop a scoring algorithm that automatically evaluates students' written justifications of diagnostic strategy. 2) Build a taxonomy of strategy failures from students' diagnostic justifications. 3) Work closely with SIUSOM and other medical schools contemplating the addition of diagnostic reasoning assessment to their curriculum. Phase II will focus on additional specific aims: 4) Develop an application based on the Phase I proof of concept with refined algorithms for scoring, categorizing reasoning failures and targeted remediation. 5) Evaluate the learning application for usability, acceptance via focus groups, and effectiveness via a limited field trial with students at SIUSOM. The proposed product represents a significant shift in undergraduate medical training and through Phase III dissemination will address a critical gap between education and practice in academic medicine.